The present invention relates to a facility for monitoring the carrier-frequency and sideband signals radiated by a DVOR ground station, according to the precharacterizing clause of claim 1.
A facility of this kind is described in an article by W. J. Crone and H. Popp, "Das Doppler-Drehfunkfeuer", published in the journal "Elektrisches Nachrichtenwesen", Vol. 43, Nov. 2, 1968, on pages 148 to 152.
In the DVOR navigation system, the phases of the carrier and sideband signals radiated by the DVOR ground station are set so that the specified phase relation exists in the far field. To check whether this phase setting in the far field has the correct value, a minimum distance between the DVOR ground station and the monitor antenna of 150 to 200m is necessary for prior art type monitoring facilities. With a smaller distance, the signals radiated by the DVOR ground station can no longer be monitored. Due to the short distance, the paths of the signals radiated by the individual radiators of the the DVOR ground station and picked up by the monitor antenna are not parallel as is the case in the far field. This causes transit-time differences and, consequently, phase distortions.